Thank you for your question. The part number for the carbonation cap is 4BXP1A-001. They are $4.95 each with a minimum order of 10 quantity required. If 10 is too many for you the are also available at MoreFlavor (http://morebeer.com). Just type "kent" in the search area and it will being up all of our products that they sell. Please let me know if you need anything else.